Transmission Fluid Pressure Sensor/Switch "C" Circuit Intermittent
The transmission fluid pressure sensor circuit C is experiencing intermittent electrical issues that prevent the PCM/TCM from accurately monitoring transmission fluid pressure. This can cause the transmission control module to compensate by altering shift patterns, potentially affecting performance and fuel economy.
What You Might Notice
- Transmission shifting harshly or at incorrect RPMs
- Reduced fuel economy
- Transmission entering limp mode or safe mode
- Check engine light illuminated
- Intermittent transmission performance issues that come and go
Most Common Causes
- 1
Failed transmission fluid pressure sensor
The TFPS sensor itself has failed or is degrading, causing intermittent signal loss to the PCM/TCM. This is the most common cause of P0874.
- 2
Corroded or damaged sensor connector
The connector pins to the pressure sensor are corroded, loose, or partially disconnected, causing intermittent signal interruptions.
- 3
Wiring circuit fault or break
The signal wire from the sensor to the PCM/TCM has an intermittent open circuit, short to ground, or short to voltage caused by damage or corrosion.
- 4
Internal transmission mechanical issue
A failing transmission component may be affecting actual fluid pressure, though this is less common than electrical failures.
How to Diagnose It
- 1
Check Failed transmission fluid pressure sensor — The TFPS sensor itself has failed or is degrading, causing intermittent signal loss to the PCM/TCM. This is the most common cause of P0874.
- 2
Check Corroded or damaged sensor connector — The connector pins to the pressure sensor are corroded, loose, or partially disconnected, causing intermittent signal interruptions.
- 3
Check Wiring circuit fault or break — The signal wire from the sensor to the PCM/TCM has an intermittent open circuit, short to ground, or short to voltage caused by damage or corrosion.
- 4
Check Internal transmission mechanical issue — A failing transmission component may be affecting actual fluid pressure, though this is less common than electrical failures.
How to Fix It
- 1
Inspect and clean sensor connector
Locate the transmission fluid pressure sensor connector and inspect for corrosion, damage, or loose pins. Clean the connector thoroughly with electrical contact cleaner and reseat the connection firmly.
- 2
Replace transmission fluid pressure sensor
Remove the old TFPS sensor from the transmission case using the appropriate socket and install a new OEM or quality aftermarket sensor. Torque to manufacturer specifications.
- 3
Inspect and repair wiring harness
Trace the signal wire from the sensor to the PCM/TCM connector. Check for cuts, corrosion, pinched wires, or damaged insulation. Repair or replace damaged sections and ensure all connections are secure.
- 4
Perform transmission fluid system inspection
If electrical components test normal, have a transmission specialist perform a pressure test and internal inspection to rule out mechanical failure affecting fluid pressure readings.
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